1. Field of Invention
The invention relates to LED (light-emitting diode) manufacturing, particularly, to a method of manufacturing an LED of high reflectivity, and, more particularly, to a method of manufacturing an LED having a metal reflector including an Au layer coated on an Ag layer thereof after annealing.
2. Description of Related Art
A conventional LED is schematically shown in FIG. 8. The LED comprises a substrate 51, an n-type GaN (gallium nitride) layer 52 deposited on the substrate 51, an active layer 54 deposited on a portion of the n-type GaN layer 52, an n-type metal electrode 55 on another portion of the n-type GaN layer 52, a p-type GaN layer 53 deposited on the active layer 54, and a p-type metal electrode 56 on the p-type GaN layer 53.
The above conventional LED has a low light emission efficiency.
Another conventional method of manufacturing an LED is schematically shown in FIG. 9. A produced LED is formed on an n-GaN based epitaxial layer 40. The LED comprises a metal reflector 36 including an upper Ni (nickel) layer 361, an intermediate Ag (silver) layer 362, and a lower Au (gold) layer 363 stacked together in which the upper Ni layer 361 functions as an adhesive and the Ag layer 362 acts for reflecting light, A p-type metal electrode 35 electrically interconnects the Au layer 363 and the n-GaN based epitaxial layer 40. A p-type GaN layer 33 is deposited on the metal reflector 36 to be electrically connected to the p-type metal electrode 35 through the Au layer 363. An active layer 37 is deposited on the p-type GaN layer 33. An n-type GaN layer 32 is deposited on the active layer 37. An n-type metal electrode 34 electrically interconnects the n-type GaN layer 32 and the n-GaN based epitaxial layer 40, A substrate 31 is deposited on the n-type GaN layer 32.
The Ni, Ag, and Au layers 361, 362, and 363 are annealed in a furnace to form the metal reflector 36 which is adhered to the p-type GaN layer 33.
Light emitted from the active layer 37 impinges on the metal reflector 36 prior to reflecting to the active layer 37. Thus, the metal reflector 36 of high reflectivity can increase the light emission efficiency of the LED.
However, the Au layer 363 tends to melt and, thus, permeates the Ag layer 362 in the annealing process. This can decrease reflectivity of the Ag layer 362, resulting in a decrease of the light emission efficiency of the LED.
In addition, there have been numerous suggestions in prior patents for the manufacturing of an LED. For example, U.S. Pat. No. 7,279,347 discloses a method for manufacturing a light-emitting structure of a light-emitting device (LED).
Thus, it is desirable to provide a novel method of manufacturing an LED in order to overcome the inadequacies of the prior art.